To expand the applications of organic electroluminescent devices (hereinafter also referred to as organic EL devices), active research has been conducted seeking development of materials with phosphorescent compounds having high luminance efficiency. In particular, for organic EL devices to be used in displays, materials are required to show high luminance efficiency and ensure stable and long performance of the devices.
Patent Document 1 discloses a luminescent polymer material that has a phosphorescent iridium complex as a side chain of the polymer. The iridium complex has two phenylpyridine ligands and one β-diketonate ligand coordinated to an iridium atom, and the β-diketonate ligand is bonded to the polymer main chain. The luminescence from the iridium complex is probably attributed to electron transition between the metal and the phenylpyridine ligands or within the phenylpyridine ligands.
Patent Document 2 discloses a phosphorescent iridium complex (and a polymer thereof) that has two phenylpyridine ligands and one β-diketonate ligand with a polymerizable functional group. This polymerizable iridium complex affords polymers similar to those described in Patent Document 1.
Patent Documents 3 and 4 disclose luminescent polymer materials wherein a tris(phenylpyridine)iridium complex structure that is a side chain provides phosphorescence emission. The light emission is probably attributed to electron transition between the metal and the phenylpyridine ligands or within the phenylpyridine ligands. It is possible that all the three phenylpyridine ligands may be involved in the light emitting.
However, organic EL devices manufactured using the luminescent materials of Patent Documents 1 to 4 are still unsatisfactory in luminance efficiency and durability.
Patent Document 1: JP-A-2004-531850
Patent Document 2: JP-A-2004-526024
Patent Document 3: JP-A-2002-293830
Patent Document 4: JP-A-2006-8996